FIG. 1.

(A) DNA breaking and joining reactions involved in integration. Two nucleotides are removed from the viral cDNA end in the terminal cleavage step (left), then the recessed 3′ hydroxyl generated by cleavage is used to attack a phosphodiester in the target DNA, joining the viral DNA end and cleaving the target (right). Disintegration is the reversal of the strand transfer step. (B) Diagram of the microtiter plate assay for disintegration. The disintegration reaction covalently links a biotin-modified DNA strand to digoxigenin-modified strand. The resulting strand can be captured on a streptavidin-coated microtiter plate and quantified with an antidigoxigenin ELISA. HRP, horseradish peroxidase.